1. Field of the Invention
The present invention relates to orthodontic brackets that are easily positioned at orthodontically correct locations on the patient's teeth to effectively perform orthodontic treatment.
2. Description of the Related Art
In orthodontic treatment, orthodontic brackets made of metal or the like are bonded to the patient's teeth through bonding agent; the orthodontic brackets are fastened by a thin archwire; and an external force is applied to the orthodontic brackets through the archwire to move the teeth subjected to treatment to correct locations.
When an orthodontic bracket is bonded to the patient's tooth, as shown in FIG. 7, a vertical center line 85 of a bracket 84 should be overlapped with a facial axis of a clinical crown (hereinafter referred to as “FACC”) 81, and a base point 88 that is the point where a line passing the center 86b of the base 86a of the archwire slot 86 and vertical to the base 86a crosses the base 87 of the bracket 84 should be coincided with a mid-transverse plane 82. If the bracket 84 is not positioned properly as described above, load of an archwire cannot be applied properly to the tooth through the bracket 84, resulting in insufficient orthodontic treatment.
In order to overlap the vertical center line of the bracket to the FACC, a variety of brackets with markers have been used. Meanwhile, in order to coincide the base point of the bracket to the mid-transverse plane of the tooth, for example, a gage partially fixed to an archwire slot of the bracket is used to bond the bracket to the tooth with the distance between an incisal margin or a cusp of the tooth and the slot being measured by the gage. However, since the base point of the bracket and the surface of the tooth are apart from each other, and manners abutting the gage to the teeth should be changed in accordance with the position of the tooth in a row of the patient's teeth, it is not easy to coincide the base point of the bracket to the mid-transverse plane of the tooth with the gage.
On the other hand, Japanese Patent Publication (Unexamined) No. Heisei 8-112293 discloses an orthodontic bracket that can be bonded to a correct position, which is parallel to the FACC and the occlusal plane. This bracket is provided with a visible standard line, which is to be parallel to the FACC, on the center line of a pair of tiewings, and another visible standard line, which is to be parallel to the occlusal plane, on a slot line crossing the former standard line. Then, orthodontists can adjust the location of the bracket while positively utilizing the standard lines.
As described above, when a bracket is mounted to a tooth, it is necessary to coincide the vertical center line of the bracket to the FACC as well as the base point to the mid-transverse plane. But, it is not easy to do so with the above-mentioned gage. With the bracket shown in the above document, standard lines are provided on the center line of a pair of tiewings and on the slot line only, so that it is not easy to coincide the base point of the bracket and the mid-transverse plane of the tooth with each other.
Especially, as illustrated in FIG. 8, when a torque-in-face-type bracket is used, in order to coincide a base point 98 of a bracket 90 to a mid-transverse plane 92 of a tooth 96 to be treated, it is necessary to coincide the base point 98 to a facial-axis point (hereinafter referred to as “FA point”) 94 where the FACC of the tooth 96 and the mid-transverse plane 92 cross with each other. However, since the FA point 94 and a line passing the center 99b of the base 99a of the body 99 and vertical to the base 99a are remarkably apart from each other, it is not easy to coincide the base point 98 of the bracket 90 to the FA point 94.